Looks like an European Rock Dove - known as a "pigeon".

Mourning doves make a smooth cooing sound (kind of mournful) - pigeons have a "gurgly" sound to their call.

When the ERDs are pure white, they become our Peace Doves.

My dad was a bird fan, and I found this out from him.

My biggest worry is that, in cities, pigeons are often nuisance birds, and fed poisoned food - and any animal that eats the poisoned pigeons can get very sick(at the least).

If Bella was able to catch it - either it was very tame, or already injured.

HUGS to you.